Synchronizing corrector circuit



Jam, M mm R. G. sgzI-ILILER III? SYNCHRONIZING CORRECTOR CIRCUIT Filed June 27, 1945 2 Sheets-Sheet l 44 FSTANDARD FREQUENCY- m3 I GENERATOR I OSCILLATOR f CIRCUIT 43 I I II Li? .I

, RECEIVING DISTRIBUTOR LIMITER AMPLIFIER LIMITER AMPLIFIER DIFFERENTIAL I AMPLIFIER I42 INVENTOR REGINALD G. SCHULER ATTORNEY atented Jan. 31

UNITED STATES PATENTOFFICE SYNCHRONIZINGiiiifiECTOR CIRCUIT Reginald G. Schiller, Highlandilalrk, I ll., assignoi' to TeIetypefCor'poration, Chieago, 111., a corporation of Delaware Application June27, 1945, Serial No. 601,818

4 Claims. (01. its-69.5)

The present invention relates to multiplex telegraph systems, anclmore particularly to corrector circuits to be utilized therewith.

In the operation of multiplex telegraph systems, it is necessary to provide means to correct the speed of the receiving distributor with respect to the incoming line signals, so as to assure that the distributor and the incoming impulses are synchronized.

Such speed correction has previously been made by means of a tuning fork controlling the distributor driving means. While such corrector circuits have worked satisfactorily it has been necessary to spend considerable time in the manual adjusting of the tuning fork in order to automatically obtain the necessary correction. Likewise, such adjusting must be made repeatedly. Further, expensive automatic speed control equipment is necessary.

Accordingly, an object of the present invention is to provide corrector means which operate satisfactorily and with a minimum or maintenance.

A further object of the invention is to provide a crystal controlled distributor driving means which is varied by means of a comparison of the received signals and the driving means.

Another object of the invention is to provide corrector means comprising inertialess relays.

A still further object of the invention is to prep vide crystal control means and means for vary ing said crystal control means in order to insure sensitive corrector means.

A preferred embodiment of the invention comprises a crystal controlled oscillator circuit at the receiving station for driving the receiving distributor, the frequency of which is controlled by means of tubes which compare the oscillator voltage with the signal impulses and in turn control a polar relay for placing a condenser in parallel with the crystal to alter the impedance of the oscillator circuit, thus altering the crystal frequency and efie'cting "correction.

A second embodiment of the invention provides a crystal controlled oscillator circuit but substitutes mechanical relays for the tubes of the preferred embodiment in a different operational manner.

A more detailed understandin of the invention may be had from the following description with reference to the accompanying drawings, in which Fig. 1 is a diagrammatic view of a preferred embodiment of the circuit and apparatus embodying the invention;

Fig. 2 is a voltage characteristic chart;

Fig. 3 is a diagrammatic view of a second em=- bodiment of the circuit and apparatus embodying the invention, and

Fig. 4 is a voltage characteristic and operational chart of the second embodiment.

The preferred embodiment of the invention is disclosed in Fig. 1, with voltage characteristic curves for this circuit disclosed in Fig. 2..

Referring to Fig. 1, the circuit, in general, comprises a standard frequency generator H which is composed of an oscillator circuit l2 which is connected to and is controlled by a piezo electric crystal l3. The oscillator circuit i2 is connected by means of a conductor I4 to a receiving distributor I6 of which it controls the speed. The receiving distributor 16 may be of any well known type or may be of an electronic variety such as disclosed in copending U. S. -ap= lication Serial No. 596,295, filed by T A. Hansen on May 28, 1945.

The oscillator circuit generates a voltage having a sine wave characteristic such as is shown as curve I i in Fig. '2. The sine wave is impressed over a conductor [B to a limiter amplifier 19 which squares off the sine wave to a voltage hav mg a square wave characteristic such as disclosed in curve 21 of Fig. 2. The square wave passes non the limiter amplifier I 9 over a can: du'cto'r 22.

A pair of triode tubes 23 and 24 are provided which are respcns-ive to'the square wave voltage from the limiter amplifier 19 in a manner which will be described hereinafter. The output or the triodes 23 and 24 is impressed on the grids or'four tetrodes 26 to 29-, inclusive, in a manner and for a purpose to be described hereinafter.

Code signals which aretransmitted from a distant station over a suitable signaling channel are received at the station shown in Fig. 1 we e conductor 3!, are passed through a limiter amplifier 32 to square up the voltage charae= teris'ti'c the event that it is not in square wave form. The output or the limiter amplifier 3'2, which has a Characteri'stichf a squared up Wave, isshown as curve 33 in Fig. '2. in the event that the incoming line s ignalsai-e ideal, from sag daring standpoint, they will havethe same characteristic and form as curve as. The limiter ainpufier'az is connecte by means of conductor 34 to a differential amplifier 36 wherein the square wave shown as 33 is altered to have a pulse wave characteristic such as is shown on curve a! or 2. A conductor lllreceii es the output of the differential amplifier 36.

A pair of rectifier tubes 38 and 39 are responsive to the pulse wave, previously mentioned, in a manner and for a purpose to be described hereinafter. The output of the rectifier tube 39 is impressed on a grid in each of the tubes 26 and 21, over a conductor M, in a manner and for a purpose also to be described hereinafter. The output of the rectifier tube 38 is impressed on a triode 42 and the output of this tube is impressed on a grid of each of the tubes 28 and 29 similarly as with respect to the tubes 26 and 21.

A polar relay indicated generally by the numeral 43 is provided which is composed of four separate windings which control an armature 44.

The output of the limiter amplifier I9 passes over the conductor 22 and through a condenser 46 to a grid 41 of the triode 23.

The tube 23 has a cathode 5| which is connected through resistor 52 to ground and which is also connected by means of a conductor 53 to a junction point 54. The circuit from the cathode 5I is completed from junction point 54 by means of a conductor 56 leading to a grid 51 of the tube 28 and also by means of a conductor 58 leading to a grid 59 of the tube 26.

The tube 23 is also provided with an anode 6| which is connected over a conductor 62 to a junction point 63. The junction point 63 is connected through a resistor 64 to positive grounded battery 66 and over a conductor 61 and through a condenser 66 to a grid 69 of the tube 24.

The tube 24 is provided with an anode 12 which is connected by means of a conductor 13 to grounded positive battery 14. The tube is also provided with a cathode 16 which is connected through a resistor 11 to ground and which is also connected by a conductor 18 to a junction point 18. The circuit is completed from the junction point 19 by means of a conductor BI which connects the conductor 18 to a grid 82 of the tube 26 and by a second conductor 83 which leads to the grid'84 of the tube 21.

Each of the tubes 26 to 29, inclusive, is provided with a cathode 86 which is grounded over an obvious circuit and with an anode 81 which L is connected by means of conductors 88 to 9|, inclusive, respectively, to one of the four windings 63 to 96, inclusive, of the polar relay 43. The opposite sides of each of the windings are connected over a common conductor 98 to positive grounded battery 99.

a The stationary or pivoted end of the armature 44 is connected by means of a conductor IIII to a condenser I02 which is connected to and in parallel with the piezo electric crystal I3, referred to previously. The movable or left-hand end of the armature 44, as viewed in Fig. 1, moves between an upper contact which is not connected in any manner and a lower contact I83 which is connected over conductor I04 to the piezo elect'ric crystal I3 and also to the oscillator circuit I2. Thus, at such time as the armature 44 is pivoted in its counterclockwise or lower position, as viewed in Fig. 1, it will be in engagement with the contact point I83 and will complete an electrical circuit through the piezo electric crystal I3 and the condenser I02.

As previously mentioned, the signal input passes over a conductor 3| to a limiter amplifier 32 and from the limiter amplifier over a conductor 34 to a difierential amplifier 36. The output of the differential amplifier 36 which is in the form of a pulse wave, as may be seen as curve 31 of Fig. 2, passes over the conductor 48 to a junction point I06. Such voltage is further impressed through a condenser I01 and over a conductor I08 to the cathode Hi9 of the rectifier tube 38, and also over a conductor III and through a condenser H2 to an anode II3 of the rectifier tube 39 and through the reistors II4 and H6 to the cathode I I1 of this tube. As may be noted, the conductor joining the resistors II4 and I i6 is grounded over an obvious circuit.

The rectifier tube 38 is connected similarly to the tube 36; that is, the anode H8 thereof is connected to the cathode I09 over a conductor IIS and through a pair of resistors I2I and I22. Likewise, the conductor H9 is grounded intermediate the resistors I2! and I 22, as may be seen by reference to Fig. 1.

The conductor H9 joining the anode H8 and the cathode I29 of rectifier tube 38 is connected by means of a conductor I23 and through a condenser I24 to the grid I26 of the triode 42. The conductor I23 is also connected through resistor I21 to the cathode I28 of this tube. The anode I29 of tube 42 is connected by means of a conductor MI and through a resistor to grounded positive battery #32. The conductor I3I and the grounded battery I32 are connected through a condenser I33 and over a conductor I34 to a junction point E36 from whence a conductor I31 is connected to a grid I38 of the tube 29 and a conductor l39 extends to a grid I4I of the tube 28. The conductor I34 is grounded through a resistor I42.

The output of the rectifier tube 39, as was previously mentioned, is impressed on a conductor M which extends from the lead of the cathode I11 of the tube to a junction point I43 from whence it is connected over conductor I44 to a grid I46 of the tube 21 and over a conductor I41 to a grid $48 of the tube 25.

As has previously been mentioned, the voltage impressed from the limiter amplifier I9 and over the conductor 22 to the grid 41 of the triode 23 is of a square wave variety, as shown as curve 2I of Fig. 2. The tube 23 is ordinarily conditioned from positive battery 66 in such a manner that upon the positive part of the square wave voltage being impressed on the grid 41 thereof, the tube will operate and will cause the output thereof to be impressed over conductor 53 to the junction point 54 and thence over the conductors 56 and 58 to the grids 51 and 59 of the tubes 28 and 26, respectively. The output voltage of the tube 23, which is impressed on the grids as just described, takes the form of a positive square wave such as shown as curve I5I of Fig. 2.

The tube 24 is likewise responsive to the incoming square wave from the limiter amplifier but instead of the output of this tube having a positive square wave characteristic, such as shown as curve I 5! of Fig.2, the output is as shown as curve I52 of Fig. 2 which is exactly opposite to that of curve I5I. The tube 24 will not be operated during the time of operation of the tube 23 because of the voltage drop across thejunction pointv 63, but instead will operate or be rendered conductive during the time that the tube 23 is not operating. Thus, it is possible to derive outputs degrees out of phase from the two tubes, as shown as curves I5! and I52, previously mentioned. The output of the tube 24 is impressed on conductor I8 to the junction point 19 and thence over the conductors BI and 83 to the grids 82 and 84 of the tubes 29 and 21, respectively.

It has now been seen that the output of the oscillator circuit I2 after passing through the racemes llimiter amplifier i9 and the tubes 23 and 24 is impressed, under certain conditions, on one of the-grids of each of the tubes to 29, inclusive. l IQWGVBIf, as previously mentioned each of these tubes has two grids therein and are so con- ;structed that the tube will not be rendered con- .ductive or operating until such time as voltage is impressed on both of the grids concurrently. Thus, the tubes 29 to 29, inclusive, will not be rendered conductive due to the output of the oscillator circuit I2 alone.

Also, as previously mentioned, the signal input from a transmitting station was impressed through a limiter amplifier 32 and a differential amplifier 36., and over the conductor 49 to the junction point I96, from whence it was impressed .on the rectifier tubes 38 and 39. The voltage impressed .on these tubeshas a pulse characteristic as shown as curve 3? of Fig. 2. Upon such yoltage being impressed on the rectifier 39, over the conductor III and through the condenser H2, the'tube operates resulting in the output thereof being impressed on the conductor 4| to the junction point I43 and thence over conductors 14 i and Ml to the grids I46 and M9 of the tubes 2'l and 29, respectively. Inasmuch as 3-9is a rectifier tube the negative part of the pulse wavefil (Fig. 2) will be eliminated and the voltage impressed on the grids I45 and M9 will have a characteristic as shown as curve I53 of Fig. 2.

Rectifier tube 38 will also receive voltage having a characteristic such as shown as curve 31 of Fig. '2, and will likewise suppress the negative half thereof and pass a voltage having a positive characteristic only similar to that shown at I53 in Fig. 2 over the conductor I23 and through the condenser I24 to the grid I29 of the triode 42. Upon such voltage being applied to the grid I25 of the tube 42 this tube will be rendered conducting and will result in the tube 42 operating and impressing a voltage which will pass from the anode I29 over the conductor l3l, through the condenser H3, and over the conductor 34 to the junction point I 36 from whence it will further pass over the conductors l3? and 39 to the grids I38 and MI of the tubes '29 and 28, respectively. The output of tube 42 will thus have the same polarity as that of tube 39, but will correspond to the opposing signal change, as'may be seen by reference to the voltage characteristic curve I54 of Fig. 2. I l Under the condition as disclosed in the voltage chart of Fig. 2; that is, that the incoming line signals such as shown as curve 33 are in exact synchronism with the oscillator voltage and the limiter amplifier I9, such as shown on curve 2|, the instant corrector circuit will not operate for correction purposes because under this condition the pair of grids in each of the tubes 26 to 29, inclusive, will not receive voltage impressed thereon simultaneously. However, in the event that the incoming line signals do not correspond exactly with the output of the standard frequency generator II a condition will exist whereby a pair of grids in one of the tubes 26 to, 29, inclusive, will have voltage impressed thereon concurrently which will result in that particular tube becoming conductive or operating, which in turn causes the associated winding of the polar relay 43 to be energized to alter the speed of operation of the oscillator circuit.

If we assume, for example, that the generated frequency and the incoming line signals do not correspond (are out of phase) in such a manner that the grids 59 and 14 8 of the tube 26 have voltage impressed on them simultaneously,

tube will operate and the output thereof will be impressed over conductor 88, through the winding of the polar relay 43, over "the common conductor .98 to positive grounded battery .99, completing a circuit. Such willresult, through the energization of the winding 95, in the armature 44 being attracted and moved in a clockwise direction, ;as seen in Fig. 1. Under thiscon- :dition the electrical circuit which previously could be traced over the armature M, the conductor llll, through the condenser I02, through the piezo electric crystal I3, over the conductor I94 and through the :contact point I93 back to the armature A l, will be broken at the contact point 193 which will result in a decrease of impedance to the piezo electric crystal I3 which causes the crystal to vibrate at .a higher frequency, thus increasing the frequency of the oscillator circuit l2. A similar condition will exist when both of the grids of the tube 28 have voltage impressed on them at the same time, resulting in the winding 93 of the polar relay 43 being energized and the armature 44 again moved in a clockwise direction.

In the event that the tubes 2'! or 29 had been rendered conducting in a similar manner as with respect to the tubes previously described, the windings 96 and 94, respectively, of the polar relay 43 would become energized (that is one at a time) which would result in the armature 44 being moved in a counterclockwise direction, as seen in Fig. 1, so as to place the movable end thereof in engagement with the associated contact point I93, thus once again establishing the electric circuit through the piezo electric circuit I3 and the condenser I 92, as previously described. Under this condition the impedance in the piezo electric crystal circuit is increased, thereby resulting in a reduced frequency vibration of the crystal I3 which results in a frequency reduction for the out.- put circuit of the oscillator circuit I 2. Under this condition the output of the circuit, as shown as curve 2| in Fig. 2. will be slowed down with relation to the incoming line signals, as shown as curve 33 (Fig. 2). Inasmuch as the separate windings 93 to 96, inclusive, are polar in variety, once one of these windings has been energized and the armature M attracted or repelled with respect to the contact point H33, it will remain in that position until such time as one of the windings which is opposite causes further movement thereof, all of which is well known with respect to polar relays.

Therefore, once the corrector circuit is operated to alter the impedance of the piezoelectric crystal circuit similar correction will be made thereto until such time as the output of the standard frequency generator II is in synchronism with the incoming line signals, at which time actual correction will cease. Such correction will be occurring continuously to keep the two voltages in synchronism and, therefore, to afford a proper operating speed for the receiving distributor I6. Inasmuch as the instant apparatus is for use in multiplex systems and the receiving distributor I6 is responsive to the signal impulses of a plurality of channels, the signal condition should be altered; that is, from marking to spacing or vice versa, relatively often. In the event that such a condition did not exist; that is, there was a continuous marking or spacing condition for a relatively long period of time, no correction would occurover this period because for the operation of thetubes 26 to 29, inclusive, it isnecessarythat .7 there be a curfent'reversal or change from marking to spacing (or vice versa) condition unless the conventional polarity changes are utilized be- .tween channels or impulses in a channel.

From the above description it may be seen that the present corrector circuit will operate constantly to cause the synchronism of the distributor operating means and the incoming code signals through the apparatus utilized herein. Further, it is to be noted that inasmuch as a piezo electric crystal is used to control the frequency of the oscillator circuit I2, the oscillator circuit will ordinarily be kept within a very narrow band of frequency change.

While particular tubes have been disclosed and specific connections therefrom described, it is to be understood that the present invention is not limited to the exact connections or apparatus shown but instead may be operated with any mechanism or parts which will provide a satisfactory operation thereof.

Referring now to Fig. 3, a second embodiment of the invention may be seen which is provided with mechanical relays, rather than inertialess relays in the form of tubes, as has been described above. Fig. 4 shows operational curves for various elements and voltage characteristics of the second embodiment.

The second embodiment includes a standard frequency generator indicated generally by the numeral I6I which comprises an oscillator cir cuit indicated generally as I 62 which is controlled by a piezo electric crystal I553. The output of the standard frequency generator IGI is impressed on a conductor I 64 to a receiving distributor indicated generally as I 66, which it controls. The output of the standard frequency generator I6! is also impressed on a conductor I6I to a limiter amplifier I63 whereat the generated wave is squared off, such as shown as curve 203 in Fig. 4.

The square wave output of the limiter amplifier I68 passes over a conductor I69 to the lefthand winding of a polar relay I'll, the right-hand. winding of which is grounded at II2. An armature I73 of the polar relay III is connected by a conductor IN to the armature I76 of a polar line relay Ill. The left-hand winding of the line relay IT! is connected to a signal input I18, whereas the right-hand winding is grounded at 119. The armature I16 moves between a lefthand contact point which is connected to posi-' tive grounded battery tall and a right-hand contact point which is connected to negative grounded battery I 82.

The armature I13 of the relay III moves between a left-hand contact point which is connected by a conductor I83 to one winding of a polar relay I84 the opposite winding of which is grounded at I86, and a right-hand contact point which is connected by a conductor I8! and through a condenser I88 to an armature I89 of the relay I84.

The armature I89 of the relay I84 moves between a left-hand contact point which is connected by a conductor I9I to a winding I92 of a polar corrector relay !93, and a right-hand contact point which is connected by a conductor I94 to the opposite winding I96 of the corrector relay I93. The two windings i92 and I96 are both connected to grounded positive battery I91.

' The corrector relay I 93 is provided with an armature I98 which is connected at its pivoted end by a conductor I99 and through a condenser 20I tothe oscillator circuit I62. The movable end of the armature I98 moves between a left-hand contact point which is unconnected and a righthand contact point which is connected by a conductor 202 to the oscillator circuit I62. The piezo electric crystal I63 is connected across the conductors I99 and 202 in such a manner as to be between the condenser 20I and the oscillator circuit I62. The condenser 20I is in parallel with the iezo crystal I63. It should be noted, however, that other connections are possible, crinductors may be used, any alteration of the impedance of the circuit suiiicing.

The incoming line signals from the distant transmitting station, which comprise the signal input and which are directed over the conductor I79 to the one winding of the line relay I", take the form of a square wave, such as 204 of Fig. 4, assuming an ideal condition. If they are in phase with the output of the standard frequency generator IBI a condition will exist where the two wave fronts and ends will compare, as may be seen at the start of the curves 203' and 204 of Fig. l, which signifies synchronism. j

Referring further to Fig. 4, the curve 206 discloses the condition of the switching relay I84 with respect to the other elements, whereas the curve 201 showsthe condition of the condenser I30 and the curve 208 shows the condition of the corrector relay I93. The curve 203, described as the squared off and amplified output of the stand ard frequency generator I6I is also indicative of the condition of the relay III, whereas the curve 20-; which shows the input signals also signifies the condition of the line relay I I1.

Prior to a description of the operation it should be noted that an assumption has been made that when the winding I96 of the corrector relay I93 receives a negative potential it will cause the armature I98 to move to the left and when it receives a positive potential it will cause the armature to move to the right. Likewise, when the winding I92 receives a positive potential it will cause the armature I98 to move to the left whereas when it receives a negative potential it will cause it to move to the right.

In considering the operation of the corrector circuit let it be assumed that the previous condition has been such as to cause the armature I98 of the corrector relay I93 to be toward the left in engagement with the unconnected contact point.

In the following description of the operation reference should be made to Fig. 4, as well as Fig. 3, inasmuch as the description is based on the standard frequency pulses with respect to the line signals, as seen as curves 203 and 204, respectively. As may be seen by reference to these curves the initial condition to be described is when the frequency pulses and the signal impulses are in syn chronism, that is, their wave fronts and ends coincide from a time standpoint.

The alternate positive and zero conditions o the square wave generated by the standard frequency generator I6I operates the polar relay I I I in such a manner as to cause the armature I73 thereof to be moved to the left during the positive portion of the wave and toward the right during the zero portion of the wave. Therefore, during the first positive portion, labelled A, the armature I13 will be toward the left and in engagement with its associated contact point connected to the conductor I83. At the same time, under the assumed conditions of curve 204 (signal impulses) of Fig. 4, it may be seen that a marking or negative condition exists on the signal input line I18, which causes the line relay I" to operate and move the armature I18 to the rightyif' It previously was not in this position. An electrical circuit may be traced. from negative grounded battery I82, through the armature I19 of the line relay I11, over the conductor I14, through the armature I13 of the relay I1I (now toward the left), over the conductor I83 to the winding of the relay I 84 and to ground I86. A negative condition on the relay I84 causes the armature I89 thereof to be moved toward the right, conditioning an electrical circuit over the conductor I94- to the winding I96 of the corrector relay I93 For illustration purposes curve 288 of Fig. 4shows the condition of the relay I84, the downward drop at the start of the curve signifying that the armature I89 has moved toward the right.

During the above condition, with the armature I 89 toward the right, no circuit will be established to affect the winding I88 of the corrector relay I93 as the conductor I81 and condenser I88 connected to the armature I89 are not in contact with the armature I'IB of the relay I1I, as this armature is in its leftward position. If it is assumed that the condenser I88 has previously been charged negatively its curve will appear at this time as a straight line, as seen at the initial portion of curve 281 of Fig. 4. Inasmuch as the relay I93 is not effected and its armature I98 remains toward the left against the unconnected contact point its curve will also appear as a straight line, as at the initial portion of curve 288 of Fig. 4.

The corrector frequency pulse will now change from a positive to a zero condition, as indicated as B interval on the curve 283 of Fig. 4. As a. result of such change the relay I1I will be operated to cause the armature I18 thereof to move to the right. An electrical circuit may now be traced from negative grounded battery I82, through the armature I16 of the line relay I11 (which remains toward the right), over the conductor I'M and through the armature I13 which has just moved to the right, over the conductor I81 and through the condenser I88, through the armature I89 of the relay I84 which remains toward the right as the circuit for the relay I84 was broken by the clockwise movement of armature I19, over the conductor I98 to the winding I98 of the corrector relay I93, and thence through battery I91 to ground. As negative potential is applied to the winding I98, the armature remains toward the left in engagement with the unconnected contact point. Inasmuch as the line relay I11, the switching relay I88, the condition of the condenser I88, and the corrector relay I83 were not altered, their curves 294, 298, 28 1, and 288, respectively, remain as straight lines, as may be seen in Fig. 4.

In the next existing condition the frequency pulse is again reversed, this time from zero to a positive value, as illustrated as C on curve 888. This results in the relay I1I operating to move its armature I13 to the left, as initially described. However, the initially described condition does not exist at this time as the incoming signal im pulse has changed from a negative marking condition to a positive spacing condition, as shown on curve 294 of Fig. 4. This results in the armature I18 of the line relay being moved toward the left, thereby engaging the left contact point and connecting the armature to the positive grounded battery I 8|.

An electrical circuit may now be traced from positive grounded battery I BI, through the armature I18 and over the conductor I'M, through the armature I13 of the relay III, which has 10 moved to the left, over the conductor I83, and through the winding of the relay I84 to ground I86. The positive potential passing through the winding of the relay I84 will cause it to operate and move its armature I89 toward the left, as may be noted by the curve 288 rising at this point. The winding I92 of the corrector relay I93, which is now connected to the armature I89 over the conductor I9I,wil1not-be effected at this time, as the armature I13 is not connected to the conductor I81 and so no electrical circuit is established. Likewise, the condenser I88 is not affected, and therefore the curves 281 and 288 remains as straight lines.

Thereafter, the standard frequency will again change from a positive value to zero, as seen as D on curve 283, and the relay I1I will be operated to causeits armature I13 to move to the right. The condition of relay I88 will not be affected, as the armature I13 no longer is connected to the conductor I88. Anelectrical circuit may now be traced from grounded positive battery IBI, through the armature I16 of the line relay I11, over the conductor I14, through the armature I13 of the relay "I, over the conductor I81 and through the condenser I88, which will pass positive potential as it was negatively charged, through the armature 189 of the relay I84, over the conductor I'9I, through the winding I92 of the relay I93, and through grounded battery I91. Inasmuch as the winding I92 receives a positive potential the armature I98 of relay I93 will remain toward the left, engaging the unconnected contact point. As the relay 184 did not change during this interval its curve 298 remains asa straight line, as does the curve 288 of the also unoperated corrector relay I93. However, as the polarity was reversed with respect to the condenser I88, and it passes potential therethrough; its curve 201 will rise, as may be seen in Fig. 4.

Following the spacing impulse another negative marking impulse is received, as may be seen on curve '294 of Fig. 4. During the initial part of this impulse the line relay I11, relay Ill, and relay I84 will operate as has been described previously. Likewise, the corrector relay I93 will not be affected, and the armature I98 thereof will remain positioned toward the left. Also, during this interval the condenser I88, will not be affected. as the armature I13 of the relay "I is positioned toward the left.

During thev latter part of the signal impulse,

which coincides with interval .E of the frequency curve 293, Fig. 4, the relay I1I will operatefto position the armature I13 toward the right, An electrical circuit may then be traced from grounded negative battery I82, through the armature I 18 and over the conductor I14 to the armature I13 of therelay I1I, through this armature, over the conductor I81 and through the condenser I88, causing the condenser to pass current as the polarity of the potential is now reversed to that previously charging the condenser. Such condenser change may be seen by reference to curve 281, Fig. 4, where the curve drops to its originalvalue. The circuit may befurther traced through the armature I89 (now toward the right), over the conductor I94, and through the winding I99 of the corrector relay I93 to ground. This relay is not affected, however, as a negative potential on the winding I98 causes the armature I93 to be moved toward the left, in which position :it is already resting.

By comparing the curves 203 and 284 of Fig. 4 it. may be seen that the line signal ends prior to the end of the E frequency pulse or interval. This shows that the two waves are no longer in synchronism, but instead, that the line impulse is slow with respect to the frequency pulse generated. The change of the line signal impulse at this point from negative marking to positive spacing causes the line relay I11 to operate and position the armature I18 toward the left and thus connect it with positive grounded battery I8 I. An electrical circuit may now be traced from positive grounded battery I8 I through the armature I16 and over the conductor I14, through the armature I 13 of the relay I1I (now positioned to the right), over the conductor'l81 and through the condenser I88, which passes potential because it is of reversed polarity as may be seen on curve 201 of Fig. 4, through the armature I88 of the relay I84 (now positioned toward the right), over the conductor I94 and through the winding I96 of the corrector relay I93 to ground. The positive potential through the winding $96 will cause the relay I93 to operate to position the armature I98 toward the right. This is shown by the rise in the curve 288 of Fig. 4.

Upon the armature I98 moving to the right an electrical circuit is established which may be traced from the oscillator network I82, through the condenser 28I, over the conductor I99, through the armature I98, and over the conductor 292 back to the oscillator circuit I82. As was previously mentioned, the condenser 28I is in parallel with the piezo electric crystal I63, and thus varies the impedance of the crystal circuit. Such condition results in a decreased vibration of the crystal I93 which causes a change in the pulses generated by the standard frequency generator I6l. Such change will tend to slow down the pulses generated with respect to the line impulses, to allow them to regain synchronism.

As the frequency pulse changes to a positive value the armature I13 of the relay I1I will be moved to the left, thereby establishing an electrical circuit from positive grounded battery I8I through the armature I16 of the line relay I11, over the conductor I14, through the armature I13 of the relay "I, over the conductor I83 and through the winding of the relay I84 to ground I86. The relay I84 will operate to move the armature I89 to the left, as may be seen by the change of curve 288, Fig. 4. The corrector relay I93 will not be affected during this interval, as no circuit can be traced through the armature I13 to the conductor I81. and thus its curve 288 will remain at a straight line.

As the frequency pulse drops to zero the relay "I is operated to move the armature I13 to the right, thus extending positive potential to the conductor I81 and through the condenser I88, thence through the armature I89, over the conductor I9I, and through the winding 92 to ground. As positive potential previously charged the condenser I88 it will not be affected at this time. Positive potential through the winding I92 of the relay I93 normally causes the armature I98 to be moved to the right, but as it is already in that position nothing further occurs.

It may be seen by comparing curves 283 and 204 of Fig. 4, the line impulse changes from a positive spacing condition to a negative marking condition prior to the end of the zero interval of the frequency pulse, which indicates that the line signal is still slow with respect thereto. This causes the line relay I11 to operate and. move 12 the armature I18 to the right, thereby connecting it to negative grounded battery I82.

An electrical circuit may thus be traced from negative grounded battery I82, through the armature I16 and over the conductor I14, through the armature I13 of the relay I1I, over the conductor I81 and through the condenser I88, which passes potential as the polarity has reversed from positive to negative (see curve 281 for change) through the armature I89 of the relay I84, over the conductor I9I, and through the winding I92 of the corrector relay to ground. The negative potential being applied to the winding I92 causes the armature I98 to move to the right, in which direction it already is positioned. Therefore,

corrector relay 993 is not changed, and it still operates to correct as seen by the plus value of the curve 288, Fig. 4.

Shortly thereafter the frequency pulse (curve 283, Fig. 4) rises from zero to its positive value, causin the relay IN to operate and move the armature I 13 to the left. This results in negative potential passing through the armature I 13, over the conductor I83, and through the winding of the relay I 84 to ground. This causes the relay I84 to operate and to move its armature to the right, connecting it with the conductor I94. The conductor I94 is not eifective to complete a circuit at this time, however, as the armature I13 is positioned to the left. Thus, neither condenser I88 nor corrector relay I93 is affected.

Thereafter the frequency pulse drops to zero again, causing the relay I1I to operate to move the armature I 13 to the right. However, inasmuch as the condenser I88 was previously negatively charged, and as the armature I89 of the relay I84 remains toward the left, neither the condenser I88 nor the corrector relay I93 will be affected at this time.

The frequency pulse will once again rise from zero to a positive value, causing the relay IN to operate to move its armature I13 to the left. It is to be noted that the signal impulse did not change when the frequency pulse rose to its positive value, but instead changes to a positive spacing condition shortly after such change. Such a condition signifies that the frequency pulses are now fast with respect to the line signal impulses, and the latter therefore will have to be speeded up for maximum efliciency of operation. It should be understood that in actual operation the system would, in all probability, because of the crystal control of the speed, change from a slow to synchronous condition before changing to a fast condition. However, the instant example has been utilized for illustrative purposes, even though unlikely in actual operation.

As a result of the armature I13 moving to the left an electrical circuit is established which may be traced from negative grounded battery I 82, through the armature I18 of the line relay I11, over the conductor I14, through the armature I13, over the conductor I83, and through the winding of the relay I84 to ground I86. However, as the armature I 89 of the relay I84 was previously positioned toward the left, no change will occur.

At the time that the signal impulse changes from negative marking to positive spacing the line relay I11 will be operated to move the armature I18 toward the left. An electrical circuit may now be traced from positive grounded battery I8 I, through the armature I16, over the conductor I14, through the armature I13, over the conductor I83, and through the winding of the relay 504 to ground I86. As the potential applied to the winding is now positive instead of negative the armature I89 will be positioned toward the left, causing a rise in the curve 206, Fig. 4, at this point. However, as the armature H3 is now positioned at the left there can be no change of the condenser 188 or the corrector relay I93 at this time.

As the frequency impulse changes from posi tive to its zero condition the armature N9 of the relay Ill is once again moved to the right. An electrical circuit is now established from positive grounded battery 18!, through the armature I16, over the conductor ti l, through the armature 513, over the conductor I81 and through the condenser 188, which now passes potential due to the reversal from negative to positive, as may be seen on curve 208 of Fig. 4, through the armature :89, over the conductor Ni, and through the winding I92 to ground. The positive potential applied to the winding 192 causes the relay l93 to operate to move its armature l98 toward the left, to engagement with its unconnected contact point. Such movement of the armature I90 breaks the previously established corrector circuit which had placed the condenser Zlll in circuit with the piezo crystal E63, thereby reducing the impedance of the crystal circuit and causing the vibration of the crystal to speed up with a similar change to the standard frequency generator I61. The frequency pulses will now be speeded up in order to synchronize them with the incoming line signals.

By further tracing the conditions, as shown as curves 203 and 204 of Fig. 4, for the frequency pulses and the signal impulses, it may be seen that the relay I84, the condenser I88, and the corrector relay I93 will operate in accordance with the curves 206, 201, and 208, respectively.

Thus, it has been seen that the second embodiment of the invention compares the frequency pulses and the signal impulses, and automatically causes the operation of the corrector network to bring them into synchronism in the event that such condition does not exist.

While two embodiments of the invention have been shown and described, it will be understood that these embodiments are but illustrative and that various modifications may be made therein without departing from the scope and spirit of this invention.

What is claimed is:

1. In a corrector circuit, a pulse generator, crystal control means for controlling said pulse generator, a first pair of electron tubes responsive to the generated pulses, a second pair of electron tubes responsive to variable signal impulses irom a remotely located transmitter, a plurality of electron tubes under the dual control of said first pair and said second pair of electron tubes, and means for varying said crystal control means under the control of said plurality of electron tubes, whereby the output of said pulse generating means is altered.

2. In a corrector circuit, a pulse generator, crystal control means for controlling said pulse generator, a condenser for varying the impedance of said crystal control means, a first pair of electron tubes responsive to the generated pulses, a second pair of electron tubes responsive to variable signal impulses from a remotely located transmitter, a plurality of electron tubes under the dual control of said first pair and said second pair of electron tubes, and means for causing said condenser to be placed in circuit with said crystal control means under the control of said plurality of electron tubes, whereby the output of said pulse generating means is altered.

3. In a corrector circuit, a pulse generator, crystal control means for controlling said pulse generator, a condenser for varying the impedance of said crystal control means, a first pair of electron tubes responsive to the generated pulses, a second pair of electron tubes responsive to variable signal impulses from' a remotely located transmitter, a plurality of electron tubes under the dual control of said first pair and second pair of electron tubes, a relay controlled by said plurality of electron tubes, and means for causing said condenser to be placed in circuit with said crystal control means under the control of said relay, whereby the output of said pulse generating means is altered.

4. In a corrector circuit, a pulse generator, crystal control means for controlling said pulse generator, a first pair of electron tubes responsive to the generated pulses, a second pair of electron tubes responsive to variable signal impulses from a remotely located transmitter, a plurality of electron tubes under the dual control of said first pair and said second pair of electron tubes, a. relay controlled by said plurality of electron tubes, and means for varying said crystal control means under the control of said relay, whereby the output of said pulse generating means is altered.

REGINALD G. SCHULER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,934,400 Bollman Nov. 7, 1933 2,173,902 Gerth et al Sept. 26, 1939 2,246,284 Artzt June 17, 1941 2,249,435 Potts July 15, 1941 2,252,380 Kahn Aug. 12, 1941 2,258,151 Shenk Oct. 7, 1941 2,258,252 Shenk Oct. 7, 1941 2,309,622 Anderson Feb. 2, 1943 2,329,077 Nichols Sept. 9, 1943 2,350,008 Artzt May 30, 1944 2,359,649 Kahn Oct. 3, 1944 2,363,062 Hartley Nov. 21, 1944 2,371,905 Mathes Mar. 20, 1945 2,399,421 Artzt Apr. 30, 1946 

